The applicants have developed proprietary techniques (patent pending) to make accurate spectrophotometric measurements directly in whole blood in spite of its well-known light-scattering properties. Therefore, the goal of this project is to exploit this promising new technology by developing a portable, hand-held, hemoglobinometer-a spectrophotometric instrument capable of measuring the total hemoglobin concentration in a sample of unaltered, whole blood. An enormous demand exists for inexpensive hemoglobinometers, but those presently available suffer from many shortcomings. Some can be used only by skilled operators because they require accurate dilutions of the blood sample, often with toxic reagents. Second, they are usually slow because the processes of hemolysis and chemical conversion of hemoglobin into cyanmethemoglobin require time. Third, they alter the cellular and chemical composition of the sample rendering it unfit for further hematological analyses. By exploiting this new technology, the proposed instrument would avoid all of these problems by making its measurements directly in whole blood. Thus, the proposed hemoglobinometer would be so simple, fast, direct, nondestructive, and inexpensive that it would easily compete with the existing state of the art. During Phase l, the applicants developed a prototype and demonstrated conclusively that the new technology yields accurate measurements of the hemoglobin concentration even when the optical properties of whole blood were deliberately changed over wide ranges. The chief aims of Phase Il are to miniaturize the prototype to a hand-held size, test it extensively, and develop calibration procedures.